If we can remember this
correctly, a statistician once showed an apparently convincing statistical
relationship between the number of divorces annually in the US and the size of
the apple crop in China, as being a good example of a non-causal relationship.
Cause and effect we are more used to getting heads ‘round - but the less direct
tendency effects of causality are a bit more tricky to comprehend, and now we
might an example of the latter to worry about.

The development of enlarged
breasts (idiopathic prepubertal gynecomastia) in five boys aged four to seven
who had been exposed to tea tree oil and lavender oil in OTC health products
(soaps, shampoos), was reported by Derek Henley &
Edward Reiter of the National Institute of Environmental Health Sciences,
Research Triangle Park, N.C. & Bay State Children's Hospital, Springfield, Mass.
USA at a presentation to the Endocrine Society’s 20th Annual Meeting
at Boston on 25th June 2006. The authors also tested both oils and found an
estrogenic effect on cultured female human breast cancer cells. The
story is carried at various locations on the Internet: for example at
http://www.timesonline.co.uk/article/0,,8122-2259179,00.html & at
http://www.4woman.gov/news/english/533503.htm.
The latter article reports that the author Derek Henley described exposure to
lavender & tea tree oils and gynecomastia in young boys as ‘an association’, but
stopped short of describing the relationship as ‘cause & effect’. The estrogenic
effects in boys (presumably with low circulating testosterone), which also
prevented male hormone responsiveness, are claimed to recede if the stimulus is
withdrawn. Elsewhere in a second-hand report at http://www.healthiertalk.com/viewtopic.php?p=57827&sid=a1347fd443d918b6e489fcd737ba46bf
Henley is reported to say that “the finding is the first to implicate ‘essential
oils’ from plants in gynecomastia.”

Cropwatch mailed the Endocrine
Society (July 2006), who kindly sent us the abstract of the Henley & Reiter
paper. We subsequently asked for permission to reproduce the abstract here, but
this hasn’t come through as we go to press with this newsletter. Basically we
can reveal that the human breast cancer cell line MCF-7 was used to determine
the estrogenic activity of lavender & tea tree oils in vitro, and MDA-kb2 cells
were used to evaluate the antiandrogenic activity in vitro, the results from
which the authors claim are clinically relevant to the presented cases of males
with prepubertal gynecomastia. Several Cropwatch supporters have written in
enquiring how the authenticity of the lavender & tea tree essential oils used in
the study was established, but we have no information on this at present.
Lavender oils are, of course, commonly adulterated, but tea tree oils less so,
since prospective adulterants (a-terpinene,
g-terpinene)
are not cost-effective.

Brief Background to Estrogenic
Activity of Essential Oils.

Lets try and put this finding in
context - is outcome so very unexpected?

The essential oils that
are traditionally/anecdotally associated (rightly or wrongly) with weak
estrogenic effects include clary sage, sage, fennel & anise oils. Few published
studies have been carried out in this area but Howes et al. 2002 showed
that at very high concentration some oxygenated terpenes commonly found in
essential oils could react with estrogen receptors, the significance remaining
unclear. Early studies of Zondek (1938) implicated phenyl methyl ethers as
likely estrogenic agents in fennel oil Foeniculum vulgare Mill. The later
work of Albert-Puelo (1980) indicated that anethole polymers such as the
dianethole & photoanethole were responsible for estrogenic effects in both
fennel & anise oils, although Kraus et al. (1980) was unable to confirm
the presence of this compounds in fennel oil (apparently these compounds only
occur as an impurity in commercial anethole samples). Tabanca et al.
(2004) working with various true anise oils (from Pimpinella spp.) and
using a recombinant yeast screen found that estrogenic activity was not solely
due to E-anethole. As a further reference to studies on the estrogenic
effects of fennel, the
disogenin content of the seed embryo was considered by both Fazili Fry & Hardman
(1968) and Seshadri et al. (1973) to have phyto-hormonal properties and
to emulate estrogenic activity in adult human females. In Sudan, the
galactoguogic properties of the fennel plant are used in ethnic medicine (Ayoub
& Svendsen 1981). Bone (2003) provides an interesting discussion in a monograph
on Wild Yam Discorea villosa L. used by Western menopausal women for
hormone balancing. Wild Yam contains steroidal saponins, & Bone argues that
disogenin may also be formed as a result of bowel flora metabolism of the yam
rhizome. Bone further suggests however that there is no proof that disogenin is
metabolised in the body to any steroidal hormone, but rather that steroidal
saponins may bind to receptors in the hypothalamus and exert a negative feedback
effect for estrogen control.

The berry oil of the Chaste tree
Vitex
agnus-castus
is sometimes also used for hormonal balancing by aromatherapists: especially in
post- and peri-menopausal women. There is evidence that diterpenes in the oil
cause circulating female hormone levels to change, sometimes dramatically. The
oil should therefore only be used under medical monitoring & supervision (Lucks
et al. 2002; Lucks B. 2003-4; Sorenson J. 2003).

The ethanolic
extract & essential oil of Spanish Sage Salvia lavandulifolia Vahl was
shown to possess estrogenic activity (Perry 2000) who had separately had looked
at the in vitro estrogen receptor binding properties of the major components of
the oil (Perry et al. 1996). Only geraniol (0.1-2mM <1% of essential oil)
of the five terpenoids tested was found to have any estrogenic activity.
Houghton (2004) reviewing the work concluded that the estrogenic properties of
the extract was not shown up in the compounds tested and warned of the
limitations of in vitro testing – for example an in vivo
biotransformed metabolite may be responsible for the estrogenic activity.

So….
any estrogenic activity of tea tree & lavender oils is not much supported in the
literature by historical or anecdotal observations (apart from some very loose
association with lavender), and no active substances found in lavender & tea
tree oils causing these alleged associations readily spring to mind. It will be
interesting therefore to see if the findings of Henley & Reiter can be
independently confirmed with pure essential oils 100% derived from the
named botanical source, and a direct biological mechanism derived for the
process. Further, since other common natural phytochemicals such as linoleic
acid have also been suggested as weakly estrogenic agents, it will be
interesting to see how widespread the causes of this medical phenomena might
potentially be - we are aware for example of the use of the seeds of Black Cumin
Nigella sativa L. to plump out women’s breasts in Egyptian times (Genders
1986), but we have no information on whether the essential oil of Black Cumin
has similar properties.